Recent spintronics, thermoelectrics, and quantum computing technologies often desire different types of Heusler alloys because of their extensive uses and versatile properties. Although diverse experiments and theoretical efforts have been dedicated to several Heusler alloys for understanding their key properties, no detailed work has yet been performed on the unclear features of Sc(2)NiZ (Z = Si, Ge, and Sn) Heusler alloys. So, we aimed to clarify their electronic, optical, elastic, mechanical, anisotropic, and temperature-dependent thermoelectric characteristics via density functional theory (DFT). All investigated alloys exhibit inherent metallic character confirmed by the electronic band analysis and the calculated Poisson's ratios. According to the obtained optical data, Sc(2)NiZ (Z = Si, Ge, and Sn) alloys can be used as efficient ultraviolet (UV) absorbers and proper infrared (IR) refractors. Sc2NiSi, Sc2NiGe, and Sc2NiSn alloys also demonstrate mechanical stability, ductility, machinability, and elastic anisotropy validated through the calculated elastic constants and their interrelated mechanical data. Notably, Sc2NiSn alloy exhibits the highest Seebeck coefficient with 120 mu V/K at 300 K, and can be considered as a potential room-temperature thermoelectric material.